The purpose of this proposal is to determine the coordination of the synthesis and/or modification of tubulin, aldolase and helix destabilizing proteins during the yeast cell division cycle. We have chosen to study Saccharomyces cerevisiae because it is a simple eucaryote which is most amenable to physiological and biochemical manipulations. In addition, the availability of cell division cycle mutants should provide a great advantage in the dissection of the multi-step sequence of events which make up the cell division cycle. Aldolase, tubulin and helix destabilizing protein will be purified from yeast to allow their use as internal standards for the identification of these proteins in the two dimensional electrophoretic profile of whole cell yeast proteins. In addition we will determine if helix destabilizing protein is capable of stimulating DNA polymerase A. The time of synthesis, phosphorylation and/or charge modification of these proteins will be determined by making use of synchronous yeast cultures. Using the above periodic changes in proteins involved in defined events of the cell cycle, we will examine the coordination of these changes with the overall ordered sequence of the cell cycle by use of cell division cycle mutants which block specific sequences of cell cycle specific functions.